Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

readOnlyHint=true already covers the safety profile, and the description adds substantial non-obvious behavior: externalIsCanonical requires formal external submission, requiresAppActivation is a placeholder needing in-App confirmation, phoneVerification is guest-only, and valuePreview is only for judging missing fields. These are genuine field-level behavioral disclosures. It stops short of describing the response shape or failure modes, so it falls short of a 5.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

Nearly every clause carries real information, but it is delivered as a single semicolon-chained block with no grouping, mixing pre-read guidance, attachment handling, verification rules, and agreement requirements. It is front-loaded with the primary rule, yet the density makes it hard to parse on a first read.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description compensates by explaining the semantics of several returned fields (viewer state, missingRequired, valuePreview, externalIsCanonical, requiresAppActivation, phoneVerification, canOneClick) — exactly the kind of context an agent needs to act on the response. What is missing is any statement of the overall return shape or of what happens when the viewer has no signup record.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

There is a single parameter (slug) with 100% schema description coverage that already states its origin ('取自 list_signup_feed 的 items[].slug'). The description adds nothing about the parameter but also has nothing to compensate for, which is the baseline-3 situation nudged up because the single parameter is trivially self-documenting.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

The description never plainly states 'retrieve the signup detail for one activity'; the purpose must be inferred from the first clause about reading viewer current values/status/missingRequired, plus the title. It does distinguish itself from get_signup_gaps for the multi-event case, so an agent can route correctly, but the verb+resource statement is implicit rather than explicit.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

It names the exact precondition ('报名先读' – read before signing up), an explicit alternative with its selecting condition ('多场 get_signup_gaps'), and an exclusion ('已报勿重复' – don't repeat if already signed up). It further gates downstream actions with concrete conditions (canOneClick=false and no externalUrl → cannot sign up; agreements must be shown in full first).

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.